Page 1256 - Clinical Small Animal Internal Medicine

1194 Section 10 Renal and Genitourinary Disease

UTI in dogs. In a recent study in dogs, a short‐course/ should be avoided in patients on sulfonamides or medi-
VetBooks.ir high‐dose protocol of enrofloxacin (18–20 mg/kg once cations that cause alkaline urine. Urine acidifiers added
to methenamine cause acidic urine that can also decrease
daily for three days) was as effective as traditional‐dose
amoxicillin‐clavulanate (13.75–25 mg/kg twice daily for
ics. High doses can cause irritation to bladder mucosa
14 days) in treating uncomplicated UTI. Preliminary evi- activity of fluoroquinolone and aminoglycoside antibiot-
dence suggests this may be an effective option but addi- but this is more common in people than dogs.
tional research may be necessary to incorporate this into
routine clinical practice. Prophylactic Antimicrobial Protocols
Prophylactic antimicrobial treatment involves long‐term
daily administration of low‐dose antimicrobials in order
Complicated UTI
to inhibit or minimize uropathogen growth, thus
Antibiotic treatment of complicated UTIs should be pro- decreasing the opportunity for bacterial adhesion and
longed (typically four weeks) and always based on urine colonization of the uroepithelium. Unfortunately, there
culture and sensitivity results. It is possible that shorter are no studies in dogs that have evaluated the efficacy
duration of therapy may be effective in some or all clini- and adverse effects of these protocols. Due to the risk of
cal situations, but further studies are needed to provide creating resistant infections, prophylactic, low‐dose
more specific recommendations. One week into treat- antibiotic administration should be reserved for refrac-
ment and one week prior to discontinuing antimicrobials, tory cases and then only after all attempts to resolve
reevaluation of the urine sediment can help determine correctable problems have been exhausted.
response to therapy. When effective, no bacteria or white Prophylactic, low‐dose antibiotic treatment should
cells should be observed on sediment exam. Recheck only be initiated after standard‐dose antibiotic treatment
urine culture is again recommended 5–7 days after com- has been successful (negative urine culture). Best results
pletion of therapy to confirm successful resolution of the are expected with drugs that are excreted in the urine.
UTI. Prolonged treatment of a complicated UTI may be Other considerations should include potential side‐
necessary to sterilize the urinary tract but “buying time” effects of the drug and previous culture and sensitivity
for correction of host defense mechanism abnormalities results. Commonly used protocols include fluoroqui-
is another important consideration. If host defense nolones, cephalosporins, or beta‐lactam antimicrobials.
mechanism abnormalities are not corrected, it may be The dose used should be one‐half to one‐third the thera-
difficult to clear the current infection or, more likely, the peutic daily dose administered immediately after the last
patient will experience reinfections. voiding before bedtime. This protocol is typically recom-
mended for a minimum of six months and urinalysis and
culture should be performed every 4–8 weeks. If at any
Ancillary Therapies
point during the treatment a UTI occurs, it is treated as
Ancillary therapies designed to prevent recurrent UTI a complicated UTI. Prophylactic, low‐dose therapy can
are considered in patients where breaches in host be restarted after the reinfection has been resolved.
defenses are present but are not correctable or in cases
where an underlying cause for reinfection is not identi- Cranberry Extract
fied. Care should be taken to treat any underlying infec- Proanthrocyanidins, specifically A‐type isoforms, found
tion prior to starting any prevention measures. Owners in cranberry juice inhibit E. coli attachment by blocking
should watch closely for clinical signs and be advised that interaction of bacterial P‐fimbriae with the surface of
frequent rechecks will be necessary to detect and treat uroepithelial cells. Canine studies evaluating the efficacy
any breakthrough infections. of cranberry extract (CE) are limited, but some in vitro
data show promising results. One study demonstrated
Urinary Antiseptics that E. coli in urine from dogs receiving oral CE had
The most commonly used urinary antiseptic is methena- decreased ability to agglutinate to human red blood cells.
mine which is converted to formalin in an acidic envi- Similarly, a second study demonstrated that E. coli in
ronment. Methenamine may be considered in patients urine from dogs receiving oral CE had decreased ability
with recurrent infections or those with potentially to adhere to Madin‐Darby canine kidney (MDCK) cells.
untreatable or unresolved breaches in immunity. Just as Based on these in vitro studies, oral administration of CE
with the use of cranberry extract, this prophylactic treat- may help reduce E. coli reinfections in patients with
ment is not recommended as a sole treatment for UTIs. compromised host defense mechanisms. Due to large
Methenamine should only be used in conjunction with variations of the active compound in over‐the‐counter
antibiotics for the treatment of current infections or as a products, it may be of benefit to use canine products
preventive once the previous UTI has been cleared. Use dosed according to manufacturer recommendations.